Asynclitic birth

Last updated April 11, 2024

An asynclitic birth or asynclitism are terms used in obstetrics to refer to childbirth in which there is malposition of the head of the fetus in the uterus, relative to the birth canal.^[1] Asynclitic presentation is different from a shoulder presentation, in which the shoulder is presenting first. Many babies enter the pelvis in an asynclitic presentation, and most asynclitism corrects spontaneously as part of the normal birthing process.

Fetal head asynclitism may affect the progression of labor, increase the need for obstetrical intervention, and may be associated with difficult instrumental delivery.^[2] The prevalence of asynclitism at transperineal ultrasound was common in nulliparous women at second stage of labor and seemed more commonly associated with non occiput anterior position, suggesting an autocorrection occurs in many cases.^[2]

When the self-correction does not occur, obstetrical intervention is necessary to deliver the child. Persistence of asynclitism can cause problems with dystocia, and has often been associated with cesarean births. However, with a skilled midwife or obstetrician a complication-free vaginal birth can sometimes, though not necessarily, be achieved through movement and positioning of the birthing person, and patience and extra time to allow for movement of the baby through the pelvis and moulding of the skull during the birthing process if this is safe in the circumstances. Other options include the use of vacuum-assisted delivery and forceps.^{[ medical citation needed ]}^[3]^{[ unreliable source? ]} There is no evidence to suggest that people with previous asynclitic presentation are more likely to experience it in subsequent childbirth.^[4]^{[ better source needed ]}

Diagnosis

Asynclitism can be digitally diagnosed using intrapartum ultrasound through the transabdominal cavity and the transperitoneal cavity. Intrapartum ultrasonography is regularly used during pregnancy to constantly monitor the fetal position within the mother's belly.^[5] The International Society of Ultrasound in Obstetrics and Gynecology Practice Guidelines recommend the use of intrapartum ultrasound to diagnose asynclitic births during prolonged and obstructed labors.^[6]

Asynclitism is most easily diagnosed during labor when the cervix is opened allowing the orientation of the occiput, the back of the fetal head, to be visually assessed in relation to the mother's pelvis.^[7] Posterior asynclitism is when the fetal occiput is facing the mother's spine, and anterior asynclitism is when the fetal occiput is facing the mother's belly. The most common and preferred type of asynclitism is the left occiput anterior asynclitism because the baby's head enters the pelvis in such a way that it minimizes the circumference of how the baby exits the body as much as possible. In this type of asynclitism, it allows the fetus to be in the most efficient position. The back of the fetus's head is towards the carrier's left side. Meanwhile, their face is towards the mother's right side at an angle between the hip and the spine of the mother.^[8] Posterior asynclitism can lengthen the duration of labor and cause complications.^[9] Asynclitism is most commonly discovered during vaginal exams conducted in labor. During the exam, the healthcare professional may feel the parietal bone more distinctly than others. Professionals can also use ultrasound to help identify potential asynclitism.^[10]

Occurrence

Asynclitism can occur at any time during pregnancy. Most commonly, it occurs near the end of the third trimester or during labor. At this time, the fetus becomes more developed and begins moving down the birth canal.^[11]

Causes

The exact cause of asynclitism is unknown. The shape and size of the uterus, the weight of the fetus, pelvic anatomy, and multiparity can contribute to it.^[12] Factors can vary depending on the person carrying the fetus. For example, a pregnant person with rotated hips can increase the likelihood of asynclitism. Situational factors include a short umbilical cord and unevenness of the pregnant person's pelvic floor during contractions, leading to the baby's head tipping to one side.^[4]

Asynclitism can also begin at the time of the birth. This happens when the fetus quickly comes down on the pelvic floor before straightening their head when the water breaks.^[13] This can be due to the water rushing through the pelvis too quickly; once it occurs, it is difficult to correct.

Signs and symptoms

Signs of asynclitism which may be observed without medical diagnostic equipment include visual asymmetric baby bumps, caused by the baby's head being tilted asymmetrically in relation to the mother's pelvis, or by an abnormal buildup of amniotic fluid.^[14] The mother may report symptoms of abdominal discomfort, particularly on one side, or pain on one side of the hips.^[4]

Complications

Asynclitism is common as the fetus enters through and tilts the maternal pelvis. There are three types: anterior, posterior, and lateral asynclitism.^[2] Minor asynclitism generally resolves itself and results in uncomplicated births.^[7] Minor cases present mild molding and the slight deviation of the head from the midline, but are otherwise absent of major fetal head malpositioning. In cases that present with persistent occiput posterior - in which the head is in a downward position, but facing towards the front of the abdomen - or shoulder positions, this can result in prolonged and difficult delivery and may warrant surgical intervention.^[7]^[15]

Complications can occur before, during, and after birth that affect both parent and baby. Asynclitism can lead to slower and more difficult labor, increasing stress and fatigue. If the fetus' head is not optimally positioned, this can result in dystocia, necessitating an operative delivery. Complications are associated with procedures such as operational vaginal deliveries (OVD), particularly with the use of vacuum extraction, and caesarean sections (CS).^[2] Caesarean sections can increase the risk of maternal complications, which can affect future pregnancies. These include uterine ruptures, chronic pain, hemorrhages, and bladder injury. One of the more severe complications is placenta accreta, which can lead to a life-threatening hemorrhage and peripartum hysterectomy.^[2]

Complications the baby may face include cephalohematomas, hyperbilirubinemia, and intracranial hemorrhages.^[16]^[15] Asynclitic birth can also increase the risk of birth injuries such as brachial plexus injury in which the nerves responsible for sending signals to the baby's arm are damaged, resulting in temporary or permanent numbness, weakness, or even paralysis in the affected arm.^[17] In rare cases, uncorrected asynclitism can lead to neonatal asphyxia, in which the child does not receive enough oxygen before, during, or just after birth, which can result in temporary or permanent organ damage.^[18] The mother may experience complications such as vaginal or cervical tears, excessive blood loss, infection of the placental membrane, and postpartum infections.^[19] Asynclitism can also affect the development of facial structures and nerves during pregnancy, with lifelong consequences for the child. These complications can include facial malformation, Bell's palsy, deviated septum, and facial asymmetry.^[20]

Management

Various techniques have been tried to resolve an asynclitic position of the fetus. Vacuum extraction, a delivery assistance method used for prolonged or obstructed labor, has been shown to reverse the position from the less optimal one, known as occiput posterior or occiput transverse, to the more favorable position known as occiput anterior.^[21] However, it is not the primary treatment for asynclitic births, as the effectiveness rate is not very high and vacuum extraction can lead to additional complications.^[22] Possible complications include fetal morbidity and fatality, and damage to the derma layer leading to bleeding within the brain and the layer of skin on the skull, known as cephalohematomas.^[23] Facial nerve damage and immobility are permanent consequences from intracranial hemorrhage leading to a diminished quality of life. However, when it is successful, vacuum extraction can change the position from a non-occital anterior position to an occital anterior position, which is more favorable in terms of asynclitic births.^[24] Following any medical procedure to alter the occiput position or any assisted vaginal delivery, monitoring of the neonate is extremely important as intracranial hemorrhages may be imperceptible.

Non-invasive techniques are typically the first steps when dealing with asynclitic birth. Short and quick breaths synchronized with contractions are commonly suggested by the obstetrician to help with prolonged labor with asynclitism.^[25] Positioning techniques can also employed to help the baby to rotate or descend.^[26] Examples of these techniques include the hands-on-knees position, lunging, kneeling lunge, side-lying release, and use of a birth ball. If positioning techniques do not work, healthcare professionals may attempt manual rotation, attempting to adjust the baby's position manually via the vagina.^[27]

If none of these methods are successful, the physician may consider a caesarean section to deliver the baby safely.^[28]

Along with procedural interventions, there are supportive measures that are taken to alleviate the physical and psychological trauma associated with childbirth. Supportive measures come in both non-pharmacological and pharmacological forms.^[7] For pain management, labor analgesia has been shown to be effective. Depending on the procedure, different types of anesthesia, such as pudendal block anesthesia, may be used.^[15]

Related Research Articles

<span class="mw-page-title-main">Amniocentesis</span> Sampling of amniotic fluid done mainly to detect fetal chromosomal abnormalities

Amniocentesis is a medical procedure used primarily in the prenatal diagnosis of genetic conditions. It has other uses such as in the assessment of infection and fetal lung maturity. Prenatal diagnostic testing, which includes amniocentesis, is necessary to conclusively diagnose the majority of genetic disorders, with amniocentesis being the gold-standard procedure after 15 weeks' gestation.

<span class="mw-page-title-main">Breech birth</span> Birth of a baby bottom first

A breech birth is when a baby is born bottom first instead of head first, as is normal. Around 3–5% of pregnant women at term have a breech baby. Due to their higher than average rate of possible complications for the baby, breech births are generally considered higher risk. Breech births also occur in many other mammals such as dogs and horses, see veterinary obstetrics.

Placenta praevia is when the placenta attaches inside the uterus but in a position near or over the cervical opening. Symptoms include vaginal bleeding in the second half of pregnancy. The bleeding is bright red and tends not to be associated with pain. Complications may include placenta accreta, dangerously low blood pressure, or bleeding after delivery. Complications for the baby may include fetal growth restriction.

Placental abruption is when the placenta separates early from the uterus, in other words separates before childbirth. It occurs most commonly around 25 weeks of pregnancy. Symptoms may include vaginal bleeding, lower abdominal pain, and dangerously low blood pressure. Complications for the mother can include disseminated intravascular coagulopathy and kidney failure. Complications for the baby can include fetal distress, low birthweight, preterm delivery, and stillbirth.

<span class="mw-page-title-main">Shoulder dystocia</span> Birthing obstruction complication

Shoulder dystocia is when, after vaginal delivery of the head, the baby's anterior shoulder gets caught above the mother's pubic bone. Signs include retraction of the baby's head back into the vagina, known as "turtle sign". Complications for the baby may include brachial plexus injury, or clavicle fracture. Complications for the mother may include vaginal or perineal tears, postpartum bleeding, or uterine rupture.

Prelabor rupture of membranes (PROM), previously known as premature rupture of membranes, is breakage of the amniotic sac before the onset of labor. Women usually experience a painless gush or a steady leakage of fluid from the vagina. Complications in the baby may include premature birth, cord compression, and infection. Complications in the mother may include placental abruption and postpartum endometritis.

The obstetrical dilemma is a hypothesis to explain why humans often require assistance from other humans during childbirth to avoid complications, whereas most non-human primates give birth unassisted with relatively little difficulty. This occurs due to the tight fit of the fetal head to the maternal birth canal, which is additionally convoluted, meaning the head and therefore body of the infant must rotate during childbirth in order to fit, unlike in other, non-upright walking mammals. Consequently, there is an unusually high incidence of cephalopelvic disproportion and obstructed labor in humans.

Cervical effacement or cervical ripening refers to the thinning and shortening of the cervix. This process occurs during labor to prepare the cervix for dilation to allow the fetus to pass through the vagina. While this a normal, physiological process that occurs at the later end of pregnancy, it can also be induced through medications and procedures.

A chignon is a temporary swelling caused by a build-up of bloody fluid left on an infant's head after they have been delivered by vacuum extraction. A vacuum extraction is a type of assistance used during vaginal delivery by an obstetrician or midwife when the second stage of labor, where the cervix is fully dilated allowing for fetus delivery, is stalled. It anatomically resembles regular caput succedaneum, one of two most frequently occurring birth injuries to the head, the other being cephalohematoma, a usually harmless condition where blood accumulates under the newborn's scalp after vaginal delivery.

Chorioamnionitis, also known as intra-amniotic infection (IAI), is inflammation of the fetal membranes, usually due to bacterial infection. In 2015, a National Institute of Child Health and Human Development Workshop expert panel recommended use of the term "triple I" to address the heterogeneity of this disorder. The term triple I refers to intrauterine infection or inflammation or both and is defined by strict diagnostic criteria, but this terminology has not been commonly adopted although the criteria are used.

Postterm pregnancy is when a woman has not yet delivered her baby after 42 weeks of gestation, two weeks beyond the typical 40-week duration of pregnancy. Postmature births carry risks for both the mother and the baby, including fetal malnutrition, meconium aspiration syndrome, and stillbirths. After the 42nd week of gestation, the placenta, which supplies the baby with nutrients and oxygen from the mother, starts aging and will eventually fail. Postterm pregnancy is a reason to induce labor.

Obstetrical forceps are a medical instrument used in childbirth. Their use can serve as an alternative to the ventouse method.

A vaginal delivery is the birth of offspring in mammals through the vagina. It is the most common method of childbirth worldwide. It is considered the preferred method of delivery, with lower morbidity and mortality than caesarean sections (C-sections).

Velamentous cord insertion is a complication of pregnancy where the umbilical cord is inserted in the fetal membranes. It is a major cause of antepartum hemorrhage that leads to loss of fetal blood and associated with high perinatal mortality. In normal pregnancies, the umbilical cord inserts into the middle of the placental mass and is completely encased by the amniotic sac. The vessels are hence normally protected by Wharton's jelly, which prevents rupture during pregnancy and labor. In velamentous cord insertion, the vessels of the umbilical cord are improperly inserted in the chorioamniotic membrane, and hence the vessels traverse between the amnion and the chorion towards the placenta. Without Wharton's jelly protecting the vessels, the exposed vessels are susceptible to compression and rupture.

In obstetrics, position is the orientation of the fetus in the womb, identified by the location of the presenting part of the fetus relative to the pelvis of the mother. Conventionally, it is the position assumed by the fetus before the process of birth, as the fetus assumes various positions and postures during the course of childbirth.

In obstetrics, the presentation of a fetus about to be born specifies which anatomical part of the fetus is leading, that is, is closest to the pelvic inlet of the birth canal. According to the leading part, this is identified as a cephalic, breech, or shoulder presentation. A malpresentation is any presentation other than a vertex presentation.

A cephalic presentation or head presentation or head-first presentation is a situation at childbirth where the fetus is in a longitudinal lie and the head enters the pelvis first; the most common form of cephalic presentation is the vertex presentation, where the occiput is the leading part. All other presentations are abnormal (malpresentations) and are either more difficult to deliver or not deliverable by natural means.

An obstetric labor complication is a difficulty or abnormality that arises during the process of labor or delivery.

Prolonged labor is the inability of a woman to proceed with childbirth upon going into labor. Prolonged labor typically lasts over 20 hours for first time mothers, and over 14 hours for women that have already had children. Failure to progress can take place during two different phases; the latent phase and active phase of labor. The latent phase of labor can be emotionally tiring and cause fatigue, but it typically does not result in further problems. The active phase of labor, on the other hand, if prolonged, can result in long term complications.

Operative vaginal delivery, also known as assisted or instrumental vaginal delivery, is a vaginal delivery that is assisted by the use of forceps or a vacuum extractor.

References

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